Ketone Monitoring in Gestational Diabetes: An Emerging Clinical Priority

Measuring blood ketone levels before breakfast, lunch, and dinner detects more episodes of ketosis compared to urinary ketone testing in women with gestational diabetes mellitus (GDM), according to results from the EVOKING study published on April 29, 2025, in the journal Hormones.1

This single-center, prospective observational study from Italy enrolled 101 women with GDM who had negative fasting urinary ketone tests with the aim to evaluate whether intensive blood ketone monitoring could improve the detection of ketosis in women with GDM who test negative for urinary ketones. Their mean age was 34.7 years and they had a mean prepregnancy BMI of 28.2 kg/m². All participants were assessed between gestational weeks 30 and 32 and instructed to measure blood ketone levels before each main meal. Ketosis was defined as having blood ketone levels exceeding 0.1 mmol/L in the fasting state on at least 25% of occasions or greater than 0.2 mmol/L before lunch and dinner.

Blood ketones were detected in 37.6% of participants before breakfast, 13.9% before lunch, and 11.9% before dinner. Overall, 40.6% of the women showed at least one daily episode of elevated blood ketones despite negative urinary results. The presence of fasting blood ketones showed a strong correlation with detection of ketones before lunch (correlation coefficient [r] = 0.63, p < 0.0001) and before dinner (r = 0.55, p < 0.0001), as well as a moderate correlation with mean glucose levels one hour after breakfast (r = 0.23, p = 0.02).

The authors note that women with GDM are instructed to check their ketone levels by performing a urine test before breakfast.

However, there is often a poor correlation between fasting urine and serum ketone levels, as women with moderate to high urinary ketones may have normal serum levels. This discrepancy may be due to variable renal excretion of ketones, and dehydration where the more concentrated the urine, the higher the measured ketones. It has also been observed that since urine can remain in the bladder for many hours before excretion, the urinary ketone levels likely correspond to serum ketone levels from several hours earlier.2

This study demonstrates that blood ketone monitoring identified more ketosis episodes than urine testing suggesting that current protocols may underestimate ketone presence. Routine monitoring of blood ketone levels before meals, particularly during fasting and postprandial states, may be recommended in women with GDM to gauge a more accurate assessment of metabolic status. This may help limit the potential risk of adverse fetal and maternal outcomes of ketosis.

References

1. Hormones (Athens). 2025 Apr 29. doi: 10.1007/s42000-025-00663-1.

2  Diabetes Care. 2021;44(1):280-9.